Mr Aso is believed to favour a career civil servant with management experience and political connections, while Mr Abe is open to academics with a willingness to experiment with unorthodox policies.

A government official close to the process said there was “no question that a tense discussion is occurring” between the prime minister and finance minister.

Beyond their differences over foreign bond-buying, Mr Abe and Mr Aso have diverged over whether to revise the central bank law to weaken the BoJ’s independence – Mr Abe has kept the threat alive, while Mr Aso said on Tuesday the government has “no plans” to do so.

The Japan "story" is all about a Bank of Japan that will no longer fall into its old funk. But the idea of selecting someone who will basicaly be a repeat of the past has always been a risk, especially since Japan's current government is filled with past figures, including Abe himself, who had previously been PM.